There is at present an increasing interest in the use of polymeric resins in the fabrication of electronic components such as semiconductor integrated circuits and/or supporting carriers therefor. Illustrative of such polymeric compositions are the polyimides, such as described in U.S. Pat. Nos. 3,684,592 and 3,700,497, whose properties have made them attractive of semiconductor devices or integrated circuits. These polyimides are condensation products of pyromellitic dianhydride and an aromatic diamine, characterized with properties which made them attractive for passivation of semiconductor devices, encapsulation thereof against contaminants in the ambient, and as masks for deposition of metallization in an interconnecting pattern between elements of an integrated circuit device. However, since these polyimide polymers are cross-linked, on curing by condensation reactions, the process is characterized by the evolution of volatiles which tend to form voids in the cured product which detracts from their suitability in application.
As a result, in recent development of new thermally stable polymers attention has been focused on materials which cure without evolution of volatiles. One such approach is to use an acetylene group as the curing site in quinoxaline polymers, some of which are described in U.S. Pat. Nos. 3,966,729, 4,022,746 and 4,147,868.
Another approach has been the incorporation of a biphenylene structure into the polymer chain, as discussed in A. Recca and J. K. Stille, Macromolecules 11, 479 (1978) and R. J. Swedo and C. S. Marvel, J. Poly. Sci. Chem. 17, 2815 (1979). The curing or cross-linking mechanism in this approach is believed to involve the formation of a biradical (II) when biphenylene (I) is heated to about 400.degree. C. as follows ##STR1##
Previous applications of this approach have started with the biphenyl (I) followed by a Friedel-Crafts acylation: ##STR2##
The substituted biphenylene (III) was then modified in various ways and subsequently incorporated in a polymer chain. Typical of the polymer chains are the quinoxaline polymers. However, the use of biphenylene poses a problem since it is difficult and dangerous to make.
Illustrative of other curable quinoxalines polymers or prepolymers are those discussed in U.S. Pat. Nos. 3,852,243 and 4,125,725.